cortexm_common: disable IRQ during thread_sched_idle [backport 2020.07] #14537
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A race condition is present where an IRQ is serviced between the priority increase of the PENDSV and the sleep. When the IRQ is serviced before the WFI sleep, the core will sleep until the next IRQ and the thread activated by the IRQ will not be scheduled until a new IRQ triggers. This commit wraps an IRQ disable and restore around the priority modification and sleep to prevent interrupts from being serviced until the WFI call returns. (cherry picked from commit eec7aa2)
miri64
approved these changes
Jul 16, 2020
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Backport of #14534
Contribution description
A race condition is present where an IRQ is serviced between the
priority increase of the PENDSV and the sleep. When the IRQ
is serviced before the WFI sleep, the core will sleep until the next
IRQ and the thread activated by the IRQ will not be scheduled until
a new IRQ triggers.
This commit wraps an IRQ disable and restore around the priority
modification and sleep to prevent interrupts from being serviced until
the WFI call returns.
Testing procedure
tests/test_toolsshould work on the iotlab_m3 (see tests/test_tools: fails oniotlab-m3due tocore/cpuregression #14521)tests/xtimer_periodic_wakeupshould work on the nucleo-l152 (see core: make idle thread optional #14224 (comment))Issues/PRs references
Fixes #14521
See #14224 (comment)